Nippon Telegraph and Telephone Corporation

Other

Mitsubishi Denki Kabushiki Kaisha

Mitsumi Electric Company Ltd.

Ando Electric Company

Ntt Electronics Corporation

Renesas Technology Corp.

Sekisui House, Ltd.

Eiji Yoshida

Yasushi Takatori

Takayuki Kobayashi

Yutaka Miyamoto

Etsushi Yamazaki

Koichi Ishihara

Masato Mizoguchi

Riichi Kudo

Akihide Sano

Tadao Nakagawa

Shogo Yamanaka

Satoshi Otake

Hiroki Matsumoto

Syotaro Nakajima

Yuta Ogino

Ikuo Andreas Nakayama

Eri Kawaguchi

Satomi Kudo

Kagenori Nagao

Hiroyuki Matsunaga

Akio Ichikawa

Yoshihiro Kumagai

Hideyuki Nosaka

Munehiro Matsui

Masataka Nakazawa

Yusuke Yoshida

Tatsuro Ishimatsu

Keiichi Yahagi

Hiroto Kawakami

Hirotaka Yamamoto

Rikihiro Iida

Toru Yoshino

Yosuke Takeuchi

Kengo Horikoshi

Kazushige Yonenaga

Shoichiro Kuwahara

Masatoshi Kuroda

Mikio Yoneyama

Masahiro Tachibana

Shigeru Ono

Masayuki Hirabayashi

Fumiaki Saitou

Aya Miyagi

Hiroyuki Suitsu

Yoichi Kobayashi

Yuka Asahina

Makoto Nakatani

Provided is a fence which can prevent a person from clambering over the fence while ensuring sufficient ventilation. The fence includes: a plurality of posts; a pair of plate members extending in a horizontal direction and spaced away from each other in a vertical direction; and a blocking member arranged in the space between the plate members for keeping a foot of a person from entering the space between the plate members to prevent the person from clambering over the fence, wherein a lower end of the blocking member is spaced upward from the plate member at a lower position, and defines a lower gap against an upper surface of the plate member at the lower position, the lower gap having such a dimension as to keep a tip of the foot of the person from entering the lower gap.

Fence

To enable signal position detection, frequency offset compensation, clock offset compensation, and chromatic dispersion amount estimation in a communication system based on coherent detection using an optical signal, even on a signal having a great offset in an arrival time depending on a frequency due to chromatic dispersion. An optical signal transmitting apparatus generates specific frequency band signals having power concentrated on two or more specific frequencies and transmits a signal including the specific frequency band signals. An optical signal receiving apparatus converts a received signal into a digital signal, detects positions of the specific frequency band signals from the converted digital signal, estimates frequency positions of the detected specific frequency band signals, and detects a frequency offset between an optical signal receiving apparatus and an optical signal transmitting apparatus. Moreover, the optical signal receiving apparatus detects a clock offset between the optical signal receiving apparatus and the optical signal transmitting apparatus from an interval between the estimated frequency positions of the specific frequency band signals. Furthermore, the optical signal receiving apparatus estimates temporal positions of the detected specific frequency band signals and detects a chromatic dispersion amount from a difference between the temporal positions of the specific frequency band signals corresponding to different frequencies.

Signal generating circuit, optical signal transmitting apparatus, signal receiving circuit, method for establishing optical signal synchronization, and optical signal synchronization system

A frequency domain multiplexed signal receiving method which decodes received signals that are multiplexed in a frequency domain, includes: a digital signal acquisition step of acquiring digital signals from the received signals that are multiplexed in the frequency domain; an offset discrete Fourier transform step of applying an offset discrete Fourier transform to odd discrete point numbers based on the acquired digital signals; and a decode step of decoding frequency domain digital signals in the frequency domain obtained by the offset discrete Fourier transform, and that are the frequency domain digital signals of one or more frequency channels.

Method for receiving frequency domain multiplexed signal and device for receiving frequency domain multiplexed signal

An optical modulation device including: bias power supplies that output a signal having a bias voltage corresponding to the null point of an optical modulation unit to the optical modulation unit; and synchronous detection circuits that determine whether an intensity of a QAM signal at a drift non-occurrence time where no drift occurs in the bias voltage becomes larger or smaller than the intensity of the QAM signal at a drift occurrence time where a drift occurs in the bias voltage, adjust the bias voltage to maximize the intensity of the QAM signal when determining that the intensity of the QAM signal at the drift non-occurrence time becomes larger than the intensity of the QAM signal at the drift occurrence time, and adjust the bias voltage to minimize the intensity of the QAM signal when determining that the intensity of the QAM signal at the drift non-occurrence time becomes smaller than the intensity of the QAM signal at the drift occurrence time.

Optical modulation device and bias voltage control method

An optical signal transmitter of the present invention includes: two phase modulating portions; a phase shifter which displaces carrier phases of two output lights from the phase modulating portions by &#x3c0;/2; a multiplexing portion which multiplexes two signal lights, carrier phases of the two signal lights being made orthogonal to each other by the phase shifter; a drive signal electrode portion which supplies a differential data signal to each of four paths of interference optical waveguides, each of the two phase modulating portions having the interference optical waveguides, the differential data signal having an amplitude which is equal to a half-wave voltage V&#x3c0; of the two phase modulating portions; a drive amplifier which amplifies the differential data signal to be supplied to each of the four paths of the interference optical waveguides; a data bias electrode portion which supplies a total of four data bias voltages to two arms, each of the two phase modulating portions having the two arms; an orthogonal bias electrode portion which supplies an orthogonal bias voltage to the phase shifter; a data bias power supply portion that adjusts delay times in the two phase modulating portions by applying the data bias voltages to the data bias electrode portion; an orthogonal bias power supply portion that adjusts a delay amount relative to a light output from at least one of the two phase modulating portions by applying the orthogonal bias voltage to the orthogonal bias electrode portion; a dither signal adding portion that adds a dither signal to at most three of the four data bias voltages; a dither detecting portion which detects a wave that is n-times a dither component from an output of the multiplexing portion (where n is an integer equal to or greater than one); and an orthogonal bias control portion which feeds back a detection result of the dither detecting portion to the orthogonal bias power supply portion. The orthogonal bias power supply portion adjusts the delay amount relative to the light output from at least one of the two phase modulating portions by controlling the orthogonal bias voltage to be applied to the orthogonal bias electrode portion based on feedback from the orthogonal bias control portion.

Optical signal transmitter, and bias voltage control method

A parameter of an adaptive filter is optimized so that inter-symbol interference having an amount corresponding to an inserted fixed filter remains. A digital signal processing apparatus which is included in an optical signal receiver and processes a digital signal converted from an optical signal is provided with: a linear adaptive filter which applies a dynamically controllable linear transfer function to the digital signal; a maximum likelihood sequence decoder which applies a transfer function of a transmission-path model to a plurality of signal sequence candidates to generate a plurality of reference signals, and decodes a reception signal using maximum likelihood sequence estimation which evaluates the differences between an output signal of the linear adaptive filter and the reference signals to estimate the most likely transmission time sequence; a signal regenerator which generates a signal corresponding to decoded data from the maximum likelihood sequence decoder; a feedback distortion adding filter which adds distortion that is equivalent to the transmission-path model used in the maximum likelihood sequence decoder to an output signal of the signal regenerator; and an adaptive equalization filter control block which updates a tap coefficient of the linear adaptive filter in accordance with an LMS algorithm using the difference between a target signal that is an output signal of the feedback distortion adding filter and the digital signal as an error signal.

Digital signal processing apparatus

A polarization state of a transmission signal can be changed at a high speed based on a symbol-rate By switching a first switch, a second switch, and a third switch with time, one of an X-polarized wave_I-signal as a Y-polarized wave_I-signal, a signal caused by performing logical inversion for an X-polarized wave_I-signal, an X-polarized wave_Q-signal and a signal caused by logical inversion for an X-polarized wave_Q-signal is input to a second modulator. Further, by switching the first switch, the second switch and the third switch with time, the second modulator is input one of the X-polarized wave_I-signal as the Y-polarized wave_Q-signal, the X-polarized wave_I-signal, the signal caused by performing logical inversion for the X-polarized wave_I-signal, the X-polarized wave_Q-signal and the signal caused by performing logical inversion for the X-polarized wave_Q-signal. Thereby, a polarization state of a transmission signal can be changed at high speed based on a symbol-rate speed.

Transmission method, reception method, transmitter apparatus, and receiver device

When a circuit that calculates a frequency offset using a shape of a frequency spectrum is implemented by hardware, the circuit size can be reduced. A frequency offset estimating method for estimating the difference between a carrier frequency of a reception signal and the frequency of an output signal of a local oscillator includes performing a discrete Fourier transform on a reception signal previously sampled at a predetermined sampling frequency and outputting a frequency spectrum with a plurality of frequency components, calculating an average power of the frequency spectrum, calculating a threshold by adding a predetermined value to the average power or power obtained by multiplying the average power by a constant, performing 1-bit quantization on powers of the frequency components of the frequency spectrum based on the threshold, and calculating a centroid frequency by multiplying frequencies of the frequency components by powers of 1-bit quantized frequency components, calculating the sum of multiplied products, and dividing the sum of the products by the sum of the powers of the 1-bit quantized frequency components of the frequency spectrum.

Frequency offset estimating method and frequency offset estimating apparatus

In order to compensate for chromatic dispersion caused by optical fiber transmission in a communication system with coherent detection using optical signals, specific frequency band signals are used to enable estimation of a chromatic dispersion value. The chromatic dispersion value calculating apparatus is provided with: a signal distributing circuit which distributes, into a plurality of signal sequences, an electrical digital signal converted from received optical signals of an optical signal transmitted by an optical signal transmitting apparatus, in which a known signal with concentrated frequency components of a plurality of specific frequencies is appended to a signal generated from a transmission data sequence; a plurality of frequency band pass filter circuits, each of which separating only each of a plurality of specific frequency components in which the known signal is included from each of the signal sequences distributed by the signal distributing circuit, and passing each of the specific frequency components therethrough; a plurality of power calculating circuits which are provided so as to correspond respectively to the plurality of frequency band pass filter circuits and which calculate power values of signals output from the corresponding frequency band pass filter circuits; a delay time calculating circuit which detects times at which power has the maximum value or times at which the power exceeds a predetermined threshold value, respectively from signal sequences of the power values output from the plurality of power calculating circuits, and which compares the detected times; and a chromatic dispersion value calculating circuit which calculates a chromatic dispersion value based on a comparison result of the times by the delay time calculating circuit.

Chromatic dispersion value calculating apparatus, optical signal receiving apparatus, optical signal transmitting apparatus, and chromatic dispersion value calculation method

Provided is a frequency offset estimation apparatus that appropriately estimates and compensates for a frequency offset of a received signal when estimating the frequency offset which is the difference between a carrier frequency of the received signal and the frequency of an output signal of a local oscillator. The frequency offset estimation apparatus converts the received signal sampled in advance with a predetermined sampling frequency into a frequency spectrum having N frequency components, limits a frequency band of negative frequency components from 1 to N/2 of the frequency spectrum and a frequency band of positive frequency components from N/2+1 to N of the frequency spectrum, calculates the sum of the squares of the positive frequency components of the frequency spectrum that have been subjected to frequency band limitation and the sum of the squares of the negative frequency components of the frequency spectrum that have been subjected to frequency band limitation to calculate power of the positive frequency components and power of the negative frequency components, and cyclically shifts all frequency components of the frequency spectrum in a frequency domain until the absolute value of a power difference between the power of the positive frequency components and the power of the negative frequency components is less than or equal to a predetermined threshold value, and estimates the frequency offset based on a shift amount until the absolute value is less than or equal to the threshold value.

Frequency offset estimation apparatus, reception apparatus, frequency offset estimation method, and reception method

A connection terminal includes a frame body including first and second support parts positioned to face each other; and a third support part having first and second ends connected to an end of the first support part and an end of the second support part, respectively; first elastic contact pieces provided on the first support part on a first side from which a terminal is to be inserted and having respective first contact parts configured to contact a peripheral surface of the terminal; second elastic contact pieces provided on the second support part on the first side and having respective second contact parts configured to contact the peripheral surface of the terminal and positioned to face the first contact parts; and a third elastic contact piece provided on the frame body on a second side opposite to the first side and configured to contact an end portion of the terminal.

Connection terminal and AC adapter

The present invention relates to an optical receiver, in which the transmittance of a Mach-Zehnder interferometer can be locked at a normal operation point in a simple structure and control. A transmittance detecting circuit and a minute modulation signal detecting circuit are provided in parallel after a balanced optical receiver, and a switch is selectively connectable either a minute modulation signal detecting circuit and a transmittance detecting circuit. In the initial stage of frequency pull-in, the switch is set to connect the transmittance detecting circuit to the synchronous detection circuit. If the transmittance detecting circuit detects that the transmittance of the Mach-Zehnder interferometer at the carrier frequency becomes a desired transmittance, the connection of the switch is switched from the transmittance detecting circuit to the minute modulation signal detecting circuit.

Optical receiver using Mach-Zehnder interferometer

A chain cover includes side covers each formed with a shaft hole for receiving a coupling pin of a roller chain, two top covers each having a length substantially equal to a chain pitch of the roller chain, and a coupling plate coupling the top covers adjacent to each other. The side cover at each end of the chain cover has a convexly arcuate front edge concentric with the shaft hole and a concavely arcuate rear edge similar to the front edge, and the coupling plate and two top covers cooperate to form a slat. A plurality of these chain covers can be mounted on a plurality of parallel roller chains to cover the top and sides of each roller chain and form a flat goods conveying surface between the roller chains, thereby forming a slat conveyor which is less expensive than a roller conveyor and provides excellent conveying stability.

Chain cover and slat conveyor using the same

Growing community of inventors

Yokosuka, Japan

Eiji Yoshida